FCC wants wireless mic ban at 700MHz to boost broadband

That's it for wireless mics in the 700MHz after February 17, the FCC says. It also asks whether the agency should probe wireless mic makers for "willfully and knowingly" selling the mics for illegal use.

MyCat- Sadly you got something very wrong there You are thinking wavelength, which is a little under half a meter or thereabouts for 700MHz radio waves IIRC. The transmissions being discussed are broadcast range, which can vary depending on the power involved, but in general for the spectrum discussed, the auxiliary licenses allowed for a maximum tranmission of 250mW. Not often fully exploited though as most wireles mic packs are transmitting at a range of 30-50mW so their range is actually much less.

Kualtek- You will get different responses depending on who you ask. Myself and several other engineers have been trying to repeatedly point out some technical problems that need to be addressed before this technology can be implemented safely in the spectrum in question. It is not that I am against the use of the spectrum for information transmission, be that in last mile internet or whatever. It is more that it needs to be done correctly which IMO current recommendations do not accomplish. If you do a search on Ars for 'white space' you will find many articles of varying quality from outright crud to somewhat decent, and especially in the earlier ones you will likely find some good discussion on the technical aspects often ignored in those articles.

And Matthew Lasar- THANK YOU. As you can probably guess form the email I sent Ars, I was not expecting a decent quality article on this topic, especially given the AP story that is floating around and is nearly as bad as your last article on the "Public Interest Spectrum Coalition" but I am very pleasantly surprised and I will apologize for expecting worse as you have proven me wrong on that count.

This article in particular did a good job of doing basic fact checking on the AP article and correcting many mistakes the AP article made so thank you again for that. Now please keep it up.

We have a few wireless mics for electronic news gathering where I work and they all fall in this range. Seablade, do you have any idea if they're (Sony and Shure) retunable to an allowable range? Is there even going to be an allowable range for ENG use?

Originally posted by Chrikett:We have a few wireless mics for electronic news gathering where I work and they all fall in this range. Seablade, do you have any idea if they're (Sony and Shure) retunable to an allowable range? Is there even going to be an allowable range for ENG use?

Yes no maybe so....

Ok to try to give a bit more detail, in most recent systems, FM synthesis is used to allow for retuning within a certain bandwidth. What that bandwidth is depends on the Make/Model/Band of the wireless equipment you are using. If you are firmly in the 700MHz spectrum however chances are you won't be able to retune it far enough out to be out in the clear and will need to replace it. Post up the Make/Model/Band (IE: Shure/ULX/J1) and I can see if I know it off hand or if I can find it out for you.

There are still crystal tuned units out there that are not frequency agile at all though, for them the crystal would need to be replaced in order to retune them, and even then the design of the rest of the unit may very well prevent returning to far. In the case of these units it is probably best just to go ahead and replace them. Again post up a made/model/band and I will see what I know or can find out.

In as far as a band for allowable ENG use, if you are a licensed broadcaster you fall under eligibility under Part74 to apply for auxiliary licenses for your wireless equipment, and I highly recommend you do so if you are not already licensed. Obviously you won't be able to license anything in the 700MHz spectrum anymore, but anything else you have you are still able to license in most cases.

In as far as those that don't currently fall under Part74 eligibility, and there are quite a few of us out there, that is what the second part of this is about. They are looking at possible solutions for this after having turned a blind eye for so long. So yes it appears there will be, eventually, a system set up to allow us legal operation, but there is not as of right now, and your best bet is just to stay clear of the 700MHz area.

Originally posted by swalsh76:Pretty much what I meant. I've seen considerably angst going on in a few music forums over this, deserved or not.

Well its interesting at times to watch this. On Music Forums, particularly ones that don't get people as familiar with the engineering side of things, you will find lots of angst and probably a fair amount of opposition to the concept of White Space devices. I am sure similar things happen on the broadcast side of things. The following will be from my perspective only as an audio engineer that works primarily on the live side of things, and not on broadcast.

On tech forums however you get angst in the exact opposite direction. You get people extremely anxious to get this in, and because they don't personally operate wireless mics or even watch TV in some cases they don't care about them.

Thing is for the latter group, wireless mics, com, IEMs, etc. make a larger impact on their lives than most of them matter. It is used not only in Theater, Concerts, and TV, but also in Hollywood for example, political rallies, churches, clubs, whatever.

For the former group, that group tends to fall into two categories. One is that of the musicians, and the other is that of the engineers. The former might not understand the technology and be very scared of its use, or might not be because they see the benefit int he long run. But more importantly, in the former group in recent years I have seen more of them push to use wireless as they think it will improve their show. Maybe they are right, maybe they are wrong, but in most cases when I am helping them out on other forums I tell them straight out it is better to stick with wired. Doesn't mean all of them do. As a result, on music forums there are probably more than a few folks that COULD go to wired, but don't want to for whatever reason.

On the engineering side of things however, often times wired mics are used specifically because they need to be used, and many engineers would rather have wired when they can so they don't have to deal with the headache. There is also a growing realization that the technology is coming, and there needs to be more communication in the effect of cooperation on BOTH sides(For or Against WSDs) in order to prevent it from being implemented as a giant clusterf***.

The problem comes in with the press department of both sides spewing out propaganda, which really only serves to limit that communication. It causes each side to mistrust each other, for instance on forums like this, and even moreso when articles full of technical falsities come out which is what the AP version of this story was, and the previous Ars article on the 'PISC' was, in no small part because the original complaint by the PISC was so bad. Like it there are similar things coming out of the 'against' side of things as well.

So in the end, instead of getting discussions of technical problems, we get the press sputing propaganda with a bias towards whatever they want, which the general public takes and runs with and even semi-useful discussions become rare.

The concept of using the spectrum for wireless internet access is not a bad one by any stretch of the imagination. It is just that for the primary benefit sites like Ars pick out, last mile internet access, licensed access to the spectrum would be much better for dependable access. Problem is, the prime area for licensed access was auctioned off in a spectacular failure to the incumbant largest ISPs, so no more competition will come of it.

For other uses, like replacing the 2.4 and 5 GHz bands used for wireless networks in the home and office, a dedicated band would likely be much better as well. The downside to this is you still run into the problem of to many networks in to little of a space, and this only gets compounded in apartment buildings and other areas where living spaces are confined, because of exactly why people want to use it... It has better signal propogation through walls and thus will ahve a larger range, so instead of picking up 5-15 wireless networks in my apartment like I do now, I will pick up the next building over etc. and that number will skyrocket. To be honest, this by itself makes me wonder if this(Replacing 802.11* networks) is even a good use for the spectrum, as a 2.4GHz AP will cover the average home pretty well. Then add in licensed use of this spectrum for business/corporate environments, and likely you end up with something a bit cleaner.

But no matter what, both sides need to start working together to solve the problem on a technical level instead of just spouting off propaganda in either direction. Get the technology implemented correctly from the start, instead of trying to win public opinion to get a half baked idea in.

Originally posted by JournalBot:That's it for wireless mics in the 700MHz after February 17, the FCC says. It also asks whether the agency should probe wireless mic makers for "willfully and knowingly" selling the mics for illegal use.

There's a disclaimer in every user's manual that says the buyer is responsible for complying with the law.

I have hundreds of these little transmitters and they get used in multiple cities. Our counsel has advised against applying for licenses, even though we are in the teleproduction business. The FCC is likely to provide an easier path for authorization (which is currently geared for TV stations with a handful of units). A big rental place like mine would need an entire department just to fill out the forms, which is impractical.

Frankly the manufacturers have done a terrible job of communicating this information to the buyers.

Knowledgeable folks have stuck to systems with adjustable frequencies, including ones outside the 700mhz block, but others like small churches or bands who dont know any better got the 700mhz clearance gear dumped on them by the manufacturers to clear out inventory, with zero warning that their units have a very limited use life coming up.

Of course wireless mic makers are just now bringing us spread-spectrum and digital devices, which are a very long time coming. Certain elements of the pro audio world are always 20 years behind the times.

And no worthy engineer will touch those 'spread-spectrum' or digital devices. They are not quality at all really(Touched on again at the end of this post).

In as far as churches etc. You would be surprised. One, most manufacturers stopped selling 700MHz gear in the US some time ago. Two, everything but the absolute cheapest of the cheap mic systems sold recently are tunable. Three, churches that have invested a significant amount in their audio system fall into one of two categories...

One: They hired outside to design and install the system, in which case they probably didn't get 700MHz gear as most consultants I know stopped speccing that a LONG time ago.

Two: They have someone on staff skilled enough to run their system and do repairs, as well as build out their system, and chances are they wouldn't get any 700MHz gear either.

The majority of your 700MHz gear has been in use for quite some time, and in many cases, despite what the PISC might say, it is either being phased out by most rental houses, productions, studios, etc. or already is. There are exceptions of course, but in most cases it is already being done. There are certainly churches that got their systems many years back, along with other companies, that will get caught by this, but there was no negligent or deceptive marketing there.

In as far as replacing the technology with digital, please do a search for my name and read the requirements I have posted about 6 times in previous threads for a mic system. There is a reason why analog fm synthesis is still used for mics, it is the only thing out right now that we are technologically capable of that meets those requirements satisfactorily.

I'm curious: I work in film and one specific manufacturer, Zaxcom, is pushing a 2.4GHz digital wireless transmission system. Do you have any experience with those units and do they, in general, fail or pass your requirements?

This really sucks. It took me several years to acquire all of my wireless gear... it took quite a while because it's expensive and I'm not willing to settle for the cheap (unusable) stuff, so I was patient and bought my mics one or two at a time until I now have about 16 wireless systems, at about $500 a pop, plus an IEM system at $1500. All of it operates in the 700 MHz band (Ch 54-59). So if this were to pass my gear would become useless, worthless, even though it works perfectly for my needs. Most of it has seen very little use, so it's effectively going to be around $6000 (mics + accessories + IEM) down the drain. I couldn't even resell it to try to help pay for new gear!

I understand the need for the spectrum, but we're only being given months of warning to replace our gear, not years like we've had with the TV transition. Why can't they give us a few years to make the transition so it isn't such a burden? And are low power devices really going to cause that much of a problem?

The frequency range they have proposed is also prone to more problems than the bands we're currently using. They don't seem to be taking this market seriously at all.

I don't have any personal experience with Zaxcom, but what I have heard of them matches their specs on their site pretty well. I put the Leccy units a bit over them, they(The Zaxcom) need a wider RF bandwidth then the digital over analog FM synthesis of the Leccys, have a decent, but not great bandwith, and have a larger than normal delay in their transmission. The latter part of that is probably why I have not touched them much, as that makes a much larger difference in live sound than it does in recording, though it still requires accounting for in recording.

I can't speak at all for their 2.4GHz stuff as I haven't even heard they were working on any of it. But I do know some of the other 2.4 GHz mics I won't touch. To congested of a band to use for reliable operation in general, on top of poor audio quality in specific models(Can't speak for all of them, just the ones I have heard)

Originally posted by Doug Johnson:This really sucks. It took me several years to acquire all of my wireless gear... it took quite a while because it's expensive and I'm not willing to settle for the cheap (unusable) stuff, so I was patient and bought my mics one or two at a time until I now have about 16 wireless systems, at about $500 a pop, plus an IEM system at $1500. All of it operates in the 700 MHz band (Ch 54-59). So if this were to pass my gear would become useless, worthless, even though it works perfectly for my needs. Most of it has seen very little use, so it's effectively going to be around $6000 (mics + accessories + IEM) down the drain. I couldn't even resell it to try to help pay for new gear!

I understand the need for the spectrum, but we're only being given months of warning to replace our gear, not years like we've had with the TV transition. Why can't they give us a few years to make the transition so it isn't such a burden? And are low power devices really going to cause that much of a problem?

The frequency range they have proposed is also prone to more problems than the bands we're currently using. They don't seem to be taking this market seriously at all.

Doug you aren't going to like me very much here. You had years of warning from the TV transition itself. Most everyone I know and talk to have all been planning for it since that transition as we all expected this to happen.

There is a SLIGHT possibility of being able to resell in the EU, but don't quote me on that, I would have to look it up. The EU and other countries are the reason why similar units are still manufactured at all, they need to be licensed over there just the same, but IIRC they are still legal.

In as far as the frequency range, you are correct, it will have more problems. However note that the range proposed is from the PISC, NOT from the FCC and they are looking for comments on it, so please feel free to give them your own comments.

Also though part of that proposal is to allow mic users to continue to operate below 698MHz as secondary licensed users of the spectrum. Much like we are now but licensed.

As a documentary crew you probably fall under eligibility to apply for a license via Part74 without much problem.

In as far as guarantees, no there really isn't any guarantees at the moment. That being said, you are very likely to be safe with anything under 698MHz. No guarantees of course, but you are likely enough that I just spec'd $15000 in wireless for a client that is being installed now in fact. I am driving across country starting tomorrow night to be on hand to program the DSP and EQ the system(And to get back home from a different contract.

In as far as what bands the Sennheiser stuff is, it can be ordered in different bands. This is the case with most decent wireless equipment. For instance if you go to this page...

And look in the lower right hand above the "Related Products" section, you will see a list of frequency sheets. This are for the various bands you can order the equipment in, and clicking on any of them will bring up a PDF that describes the Frequency range, and some pre-coordinated frequencies therein.

The Sennheiser stuff is pretty good, and in the range you seem to be looking at I would look at it strongly. The 300 Series is worth it if you can stretch your budget.

Where's a good place to read more about why none of this stuff is digital yet (or why what is digital already is inferior)?

As a layman, I always noticed how in the 900MHz phone world, analog was horrible, some digital was horrible, but DSS seemed to deal with all sorts of ugly situations with no problem. Clearly a phone needs less bandwidth, but I thought it was an interesting (and observable) illustration of analog vs. multiple digital audio transmission modes. DSS was clearly, without any doubt better since there was no static, multipathing seemed to not bother it, range was great, and sound quality was great (for a phone).

What happens to this type of encoding/transmission scheme at higher bandwidths that makes it worse than analog FM?

Originally posted by sporkme:Thanks Seablade. I very much appreciate the info.

Where's a good place to read more about why none of this stuff is digital yet (or why what is digital already is inferior)?

As a layman, I always noticed how in the 900MHz phone world, analog was horrible, some digital was horrible, but DSS seemed to deal with all sorts of ugly situations with no problem. Clearly a phone needs less bandwidth, but I thought it was an interesting (and observable) illustration of analog vs. multiple digital audio transmission modes. DSS was clearly, without any doubt better since there was no static, multipathing seemed to not bother it, range was great, and sound quality was great (for a phone).

What happens to this type of encoding/transmission scheme at higher bandwidths that makes it worse than analog FM?

Several things. When dealing with the digital domain, you are typically doing a A/D D/A conversion for one thing, which introduces latency. And then depending on the digital transmission used, it can be even worse with a varying latency. Also on top of all this a digital transmission, particularly DSS tends to require even more bandwidth than analog requires for a strong dependable and high bandwidth(For audio) signal.

Analog works BECAUSE it is simple. It has a guaranteed latency that is pretty well nothing at the ranges we are discussing since radio waves move so fast, and because of this the latency is extremely stable.

Gimme a bit and I will dig up my post, again, and repaste the thing here.

For people saying it should use IP to broadcast instead of FM synthesis, take a look at the latency requirements for wireless mics. The requirements would be in the range of a max of 1.5mS including AD/DA and transmission. It would also have to be 100% consistent latency within a range of a few nanoseconds. Just transmission alone on standard wireless IP is ridiculously more than that.

EDIT: I forgot to point out, this was on a completely unloaded 802.11n 2.4GHz network with both nodes(One Macbook Pro and one router) in line of sight. Can't get much more ideal conditions on wireless IP networks.

That is a hell of a range, and average latency is much to high. Even the minimum latency of the packets don't include any ad/da conversion you would need in audio, making it even worse. IP technology need not apply here, try suggesting something that works, thus far I haven't seen a good suggestion in that category.

Not only must the suggestion meet latency requirements, it must also meet quality requirements, a full 24/44.1 signal I would consider a minimum if talking digital, or a 20kHz bandwidth analog signal. It must also meet power requirements, as these are BATTERY powered equipment that must last many hours on a single battery(Or small set of batteries at most, 2AA would be the max IMO). And must meet range requirements which can easily be hundreds of feet. In fact one space I am doing an install in now has a range requirement of 130ft with multiple walls in the way on occasion at the moment.

Obviously for your topic the IP based broadcast need not apply (Thank you for not suggesting it), but the basic requirements for a wireless microphone are what you will want to take a look at very carefully. Remember in a phone conversation, you can get away with a much larger latency than you can in musical contexts. 50mS is perfectly fine for phones and most people won't even notice it most likely as they don't really have a reference, since their own voice can be a local fed loop, and for all intents and purposes people don't react fast enough for that to make a difference in normal conversation.

To be honest I am fairly sure that I have heard even worse latency, but can't prove it right now. Until you get in the range of 250mS many people won't notice it, some might around 100mS.

Now in dealing with a musical contexts, musicians can hear down to 3-5mS depending on the training of their ears. To give an example, the contract I am about to leave is with an Opera, and part of my job was maintaining a monitoring system for two operators for a titling system. One of them is a classically trained pianist, and has very good trained ears. Since I did not spec the original system it had no delay compensation at all and one microphone location for it was in the orchestra pit, while another microphone location was a good 30-35 feet above it in the grid. The delay from that is going to be about 30mS and it was bad enough to his ears he couldn't use those microphones together because it would throw him off.

For the record, the other person came from a technical theater background, and while she knew music, her ears were not quite so well trained and it didn't bother her nearly so much. But she is also not someone you probably would see performing there, whereas he could be.

It is not that the delay by itself would be so bad, but the delay with the reference, which is what you get in live music and other events(The reference is always the acoustic sound for the audience) that is the problem. That is why a phone conversation, with no reference, can get away with a much larger latency, or even a varying latency as well.

I just want to echo Seablade's comments that digital is not acceptable for wireless mic transmission, exactly for the reasons stated (latency). Various microphone manufacturers have tried digital systems in the past, and while the technical specifications as far as frequency response, noise level, etc. may look good, they are next to worthless in real-world use specifically because of the A-D-D-A conversions involved, and they have pretty much all failed.

Just about everyone would have a hard time listening to themselves with in-ear monitors if they were to use a digital wireless mic system, because psychologically it doesn't feel right at all. A friend and I tried to use IEMs with a digital mixer with a significant latency (such as would be experienced with a wireless mic system) and we wanted to rip the IEMs out immediately because it was playing with our heads too much.

It's not to say that someone, sometime couldn't come up with a digital system with low enough latency to be useful, but it just isn't the right thing to do. It would probably have to work with parallel data transmission (instead of serial) to try to overcome latency issues, which means sending and receiving like 20-24 RF channels simultaneously, or use some sort of fancy multiplexing technique. So it would be expensive and prone to problems. And it would be just plain unnecessary considering that modern professional analog systems work so well.

Originally posted by Seablade:Doug you aren't going to like me very much here. You had years of warning from the TV transition itself. Most everyone I know and talk to have all been planning for it since that transition as we all expected this to happen. Seablade

Yes, we have known about the TV transition. But the FCC has generally left low power devices alone in the past, and normally we get a grace period after a significant change in regulations.

I'm not really sure how wireless mics with a range of maybe a few hundred feet under ideal conditions would impose significant interference with long range transmissions like those scheduled for introduction into the 700MHz band, especially for people like me who use them a few hours per month at constantly varying locations. I can only assume that many devices in the new band will also use frequency hopping technologies to avoid interference as well.

The other problem is that most wireless mic manufacturers are still producing 700 MHz products. And people are still buying them. With less than 6 months of usable life in them. And generally the people selling this stuff aren't saying a word about any upcoming cutoff date. Some manufacturers are even saying their gear is compliant with new regulations when it isn't.

In the past we've had grace periods for changes like this. This one seems to be an exception. And a very costly one at that.

I'm going to start digging around on wikipedia to find out more about A/D and D/A conversion delays, it sounds like an interesting problem.

I do see lots of non-wireless digital though, even cheap stuff like Firewire A/D boxes that boast delays of but a few ms. Aren't there also now mixers and other devices that work solely in the digital realm? Are these exclusively used where there does not need to be any sync to picture or any mix for the talent?

Currently taking a break from a long day of driving back home so Ill keep this short before I get back on the road again for a few more hours before I crash for the night.

quote:

Originally posted by Doug Johnson:Yes, we have known about the TV transition. But the FCC has generally left low power devices alone in the past, and normally we get a grace period after a significant change in regulations.

That may be true, but also keep in mind that in general they turned a blind eye to wireless mics BECAUSE they could be a licensed use int he spectrum and rather than going through the rigamarole of actually changing their licensing requirements to fit the use, they turned a blind eye to it.

This is a bit different than having the low power devices that really don't act as an auxiliary broadcast device to anything using that spectrum IMO. This is why I and many others have expected this for some time.

quote:

The other problem is that most wireless mic manufacturers are still producing 700 MHz products. And people are still buying them. With less than 6 months of usable life in them. And generally the people selling this stuff aren't saying a word about any upcoming cutoff date. Some manufacturers are even saying their gear is compliant with new regulations when it isn't.

I am sorry, but this really isn't true. Off hand Shure and Lectrosonics both have stated they stopped manufacturing of wireless technology in that range last year IIRC. I am fairly certain Sennheiser is in a similar boat as well. I can't speak for all of them of course, but between those three you have the vast majority of professional wireless systems sold these days.

I guess I shouldn't say manufacturing, but rather selling in the US. They may still be manufactured, but if they are, are not intended for distribution in the US, as they are still legal in the EU with a license of course. But even then, for instance, Leccy is only making units in that range specifically by special order that is completely non-refundable now. I could still get the unit, but I would be hard pressed to do so to be honest, I have to really work at it.

quote:

I do see lots of non-wireless digital though, even cheap stuff like Firewire A/D boxes that boast delays of but a few ms. Aren't there also now mixers and other devices that work solely in the digital realm? Are these exclusively used where there does not need to be any sync to picture or any mix for the talent?

Several things to consider here though. One you have an entire DSP pipeline in those devices specifically set up to handle the processing needed for the low latency. Even with this though digital mixers still end up in the 1.5-3mS range of latency, certainly usable on their own, but chaining a lot of AD/DA together will make a noticeable difference.

Two, keep in mind you are also limited in power envelope, so you really can't add in an entire processing chain in the mix as well.